Electrical contact element



Patented at. 23,, N45 7 Litre stars s ars a earns sic annorarcsr. coarser rammar Robert H. Savage. Scotia, N. .12., assignor to. General Electric Company, a corporation of New York No g. Application December 22, E413,

Seriaihio. 5153M (Claims. (Cl. lili s-325) an improved electric brush contact element,

formed of a carbonaceous material and boron.

A further object of my invention is to provide an improved method of making a brush or carbonaceous material, such as graphite, with a boron composition.

Further objects and advantages of my invention will become apparent and myinvention will be better understood from the following description, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

Various arrangements and methods have been proposed for making electric contact elements, such as brushes, of carbon, which are strong and without an objectionabl scouring or abrasive action on the element with which they form an electrical contact. Such brushes have generally been made of graphite which is held together by a binder formed of a material such as an organic resin or pitch mixed with the graphite and then pressed and fired, or by mixing a finely divided metal, such as copper to the graphite and then pressing and sintering the mixture at a relatively high temperature to form a continuous metal skeleton or .mesh which holds'the graphite together, providing strength to the brush and also increasing its conductivity. Other binders have been used for specific purposes, but, in gengood results. This mixture should then be pressed to the desired shape and iired to provide a substantially homogeneous sintered contact element.

While I have described particular embodiments of my invention, modifications thereof will occur to those skilled in the art. I desire it to be understood, thereiore, that my invention is not to be limited to the particular arrangement disclosed,

and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric contact element formed oil a mixture of a carbonaceous material, and, finely divided boron carbide substantially all passable through a 600 mesh having the characteristics of a pressed and fired mixture of this tym.

2. An electric contact element formed of a carbonaceous material and boron carbide substantially all passable through a 600 mesh having the characteristics of a pressed and fired mixture of this type.

3. An electric contact element formed of a mixture of a carbonaceous material and 15 to 30% by weight boron carbide passable through a 600 mesh and .having the characteristics of a pressed'and sintcred together mixture of this 4. An electric contact element formed of a mixture of a carbonaceous material and 10 to 20% by weight finely divided boron carbide in the form of a substantially homogeneous sintered material having the characteristics of a pressed and fired mixture of this type.

eral, these binders have not been found to provide strength without having some adverse efiect on the conductivity, friction, or contact drop of the brush contact element.

In my improved arrangement, l have found that an electrical contact elementcomprisin a carbonaceous material, such as graphite or a mixture of graphite and a metal powder, when mixed with a composition o1 boron, such as a boron carbide, to form a. brush including the carbonaceous material and the boron as a binder of the carbonaceous material,.provides an element having a much superior strength. In making this brush, the boron material, such as boron carbide, must be finely divided, and very good results have been obtained when substantially all of it was passable through a 600 mesh and then mixed thoroughly with the finely divided graphite and where the boron carbide material formed from 10 to 20% by weight of the mixture. These proportions'are not limiting as other percentages have been used and also ha e giv n 5. An electric contact element formed of a mixture of carbonaceous material and about 20% by weight finely divided boron carbide having the characteristics of a pressed and slntered together mixture of this type.

6. The method of making an electric contact element including mixing carbonaceous material and finely divided boron, pressing the mixture to the desired shape, and sintering it to provide a unitary element.

'Z. The method of making an electric contact element including mixing graphite and a binder comprising finely divided boron carbide, pressing the mixture to the desired shape, and slntcr ing it to a homogeneous element.

8. The method of making an electrical contact element including mixing graphite and a binder comprising finely divided boron carbide through a 600 mesh, pressing the mixture to the desired shape, and slntering it to form a substan- ROBERT H. SAVAGE. 

